The present invention relates to a mechanism which interlocks a zoom lens and a focus lens and lens interlock method, camera and portable terminal having lens interlock mechanism.
In recent years, a lens system having a variable focal length, what is generally called as a variable-focal lens system, has come into wise use in place of ordinary zoom lens system. The variable focal lens system is provided with a zoom lens and a focus lens between an objective lens and an eyepiece, and these zoom lens and focus lens are mutually movable independently from each other.
In the variable focal lens system, magnification of the subject is variable. However, the focal position exceeds the focal depth by the movement of zoom lens. Therefore, during the movement of zoom lens, a subject projected on a camera and a monitor of video camera gradually becomes an out-of-focus image with the movement of the zoom lens and a desired image is not obtained.
In order to cancel the above out-of-focus, various focus correcting techniques have been known. For example, there is a technique of alternately carrying out the movement of zoom lens and the movement of focus lens, and thereby, canceling the out-of-focus during zoom operation. Moreover, there is a technique of moving the zoom lens to a desired position while allowing the out-of-focus, and thereafter, carrying out an AF (auto-focus) operation, and thereby, canceling the out-of-focus after zooming operation.
However, according to the conventional techniques, during the movement of zoom lens, it is impossible to smoothly and continuously produce an image having almost no out-of-focus.
More specifically, according to the former conventional technique, the movement of zoom lens and the movement of focus lens are alternately carried out. Thus, these lenses are intermittently operated, and a zooming operation becomes slow; as a result, time takes to move a zoom lens to a desired position. For this reason, during the movement of the zoom lens, it is slow to produce an image having no out-of-focus. Therefore, a problem has arisen such that it is difficult to smoothly and continuously produce an image having almost no out-of-focus during the movement of the zoom lens.
Moreover, according to the latter conventional technique, the zoom lens is moved to a desired position while allowing an out-of-focus, and thereafter, an AF (auto-focus) operation is carried out. Thus, as a zoom ratio becomes large, an out-of-focus becomes large with the movement of the zoom lens. For this reason, it is impossible to always produce an image having no out-of-focus. Therefore, a problem has arisen such that it is difficult to continuously produce an image having almost no out-of-focus during the movement of the zoom lens.
The above problems become more prominent because of the recent photographic style. These days, it is general practice to select an object while confirming an image of the subject projected on a camera and a monitor of video camera. In this photographic style, in order to enable a photographic object to select while confirming a subject image projected on a monitor and the like, the subject image needs to be sufficiently confirmed by the monitor or the like even during a zooming operation. Therefore, it is desired to smoothly and continuously project an image having almost no out-of-focus on a monitor or the like during the movement of zoom lens. As described above, according to the above conventional techniques, during the movement of zoom lens, it is impossible to smoothly and continuously produce an image having almost no out-of-focus; for this reason, a problem arisen such that it is difficult to meet the demands as described above.
It is an object of this invention to provide a lens interlock mechanism and lens interlock method, camera and portable terminal having lens interlock mechanism which can smoothly and continuously produce an image having almost no out-of-focus.
The lens interlock mechanism according to this present invention includes a first driving unit which directly drives at least the zoom lens; a second driving unit which indirectly drives the focus lens; and a third driving unit which directly drives the focus lens by being driven by the first and second driving unit. The first driving unit moves the zoom lens along the optical axis direction of the zoom lens while giving a first driving force corresponding to the movement of the zoom lens to the third driving unit, the second driving unit gives a second driving force corresponding to a distance between the subject to the third driving unit, the third drive unit receives the first and second driving force and thereby moves the focus lens to the optical axis direction of the focus lens while keeping a predetermined relation to the zoom lens based on the distance to the subject.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.